fix(classify): backup/heartbeat severity=warning/critical 告警恢復告警卡片格式

根因：classify_alert_early() backup 規則無 severity 條件，導致
VeleroBackupFailed / HostBackupFailed (warning/critical) 被分為 TYPE-1
（純資訊無按鈕），告警卡片格式遺失。

修復：
- backup/heartbeat 關鍵字只在 severity=info/none 才命中 TYPE-1
- severity=warning/critical 的 backup 告警走正確 prefix 規則
  (Velero→kubernetes TYPE-3, HostBackup→infrastructure TYPE-3)
- Watchdog (severity=none) 由 severity 規則先命中，維持 TYPE-1
- 補強測試：25 cases，含 VeleroBackupFailed critical → kubernetes TYPE-3

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/services/incident_service.py

@@ -126,7 +126,12 @@ def classify_alert_early(alertname: str, severity: str, _labels: dict) -> tuple[
         return "config_drift", "TYPE-4D"
     if severity in ("info", "none"):
         return "info", "TYPE-1"
-    if any(kw in alertname_lower for kw in ("backup", "heartbeat")):
+    # backup/heartbeat 關鍵字只有 severity=info/none 才是純資訊
+    # severity=warning/critical（例如 VeleroBackupFailed, HostBackupFailed）→ 繼續走 prefix 規則
+    if severity in ("info", "none") and any(kw in alertname_lower for kw in ("backup", "heartbeat")):
+        return "backup", "TYPE-1"
+    # Watchdog/Heartbeat 永遠是 TYPE-1（Alertmanager 心跳）
+    if "watchdog" in alertname_lower or alertname in ("Heartbeat",):
         return "backup", "TYPE-1"
     if alertname.startswith(("Docker", "Host")):
         return "infrastructure", "TYPE-3"

apps/api/tests/test_classify_alert_early.py

@@ -47,20 +47,25 @@ class TestInfoAlerts:
         assert nt == "TYPE-1"
         assert ac == "info"
 
-    def test_backup_keyword(self):
+    def test_backup_keyword_info_only(self):
+        # severity=info → severity 規則先命中，TYPE-1
+        ac, nt = classify_alert_early("BackupJobComplete", "info", {})
+        assert nt == "TYPE-1"
+
+    def test_backup_keyword_warning_not_type1(self):
+        # BackupJobFailed severity=warning → 繼續走 prefix 規則，不應是 TYPE-1
         ac, nt = classify_alert_early("BackupJobFailed", "warning", {})
-        assert nt == "TYPE-1"
-        assert ac == "backup"
+        assert nt == "TYPE-3"
 
-    def test_heartbeat_keyword(self):
-        ac, nt = classify_alert_early("WatchdogHeartbeat", "warning", {})
+    def test_watchdog_heartbeat(self):
+        # Watchdog (Alertmanager 心跳) severity=none → severity 規則先命中，TYPE-1
+        ac, nt = classify_alert_early("Watchdog", "none", {})
         assert nt == "TYPE-1"
-        assert ac == "backup"
 
-    def test_backup_case_insensitive(self):
+    def test_backup_critical_not_type1(self):
+        # critical backup 告警應走各自 prefix，不是純資訊
         ac, nt = classify_alert_early("BACKUP_MISSING", "critical", {})
-        assert nt == "TYPE-1"
-        assert ac == "backup"
+        assert nt == "TYPE-3"
 
 
 # --------------------------------------------------------------------------- #
@@ -100,11 +105,16 @@ class TestKubernetes:
         assert nt == "TYPE-3"
         assert ac == "kubernetes"
 
-    def test_velero_backup_keyword_wins(self):
-        # VeleroBackupFailed 含 "backup" → backup 規則優先於 kubernetes prefix
+    def test_velero_backup_failed_is_kubernetes(self):
+        # VeleroBackupFailed severity=critical → backup 規則不命中，走 Velero prefix → kubernetes TYPE-3
         ac, nt = classify_alert_early("VeleroBackupFailed", "critical", {})
+        assert nt == "TYPE-3"
+        assert ac == "kubernetes"
+
+    def test_velero_backup_success_info_is_type1(self):
+        # VeleroBackupSuccess severity=info → TYPE-1
+        ac, nt = classify_alert_early("VeleroBackupSuccess", "info", {})
         assert nt == "TYPE-1"
-        assert ac == "backup"
 
 
 # --------------------------------------------------------------------------- #